Manually set switching device

ABSTRACT

A switching device which must be manually set for operation is electrically reset to a disabled condition during operation. The device has particular utility as an emergency override for an electrical interlock system because the switching device is automatically reset to prevent a subsequent switching operation, and, conversely, permits a one-time operation. To prevent the switching device from being used to permanently defeat the electrical interlock, the switching device has &#39;&#39;&#39;&#39;trip-free&#39;&#39;&#39;&#39; operation during the manual setting procedures.

United States Patent Marcoux et al.

i 1 MANUALLY SET SWITCHING DEVICE [75] Inventors: Leo Marcoux, Rehoboth;Charles D. Pr'mary Emmmer A rthur Gr'mley Flanagan Ameboro; Thomas agirtorngy, Agenl, or lflfl'flg-JOIII'I A. Haug; James P. Evans,Rehoboth, all of Mass. rews' Russe aumann 173] Assignee: TexasInstruments Incorporated,

Dallas, Tex.

221 Filed: Dec. 5, 1973 1571 ABSTRACT [21] Appl 421389 A switchingdevice which must be manually set for operation is electrically reset toa disabled condition dur- [52] HS. Cl 337/37; 180/82 C; ZOO/61.58 B; ingoperation. The device has particular utility as an 335/186; 337/70;337/101; 337/102 emergency override for an electrical interlock system(51] Int. Cl. HOlh 39/00 because the switching device is automaticallyreset to [58] Field of Search 337/37, 39, 70, 13, 77, prevent asubsequent switching operation. and, con- 337/18. 101, 102, l 12, 113;335/186. 166, versely, permits a one-time operation. To prevent the 167.171, 164. 165, 160, 159; 340/52 E, 278; switching device from being usedto permanently de- 180/82 C, 96; 307/114, 10 AT, 10 SB; feat theelectrical interlock, the switching device has 250/6158 B; 123/179 R,179 B trip-free" operation during the manual setting proce dures. [56]References Cited UNITED STATES PATENTS 23 Claims, 22 Drawing Figures3.449.714 6/1969 Farley, Jr. 340/52 E LOGIC r A I i 1 STARTER SOLENOlDLOGIC L%J UL I SHEET STARTER SOLENOID START SOLENOID SHEET 1 MANUALLYSET SWITCHING DEVICE CROSS-REFERENCES TO RELATED APPLICATIONS Thisapplication relates to subject matter disclosed and claimed in copendingapplication Ser. No. 421 ,902 entitled Manually Set Magnetic Relay filedDec. 5, 1973, copending application Ser. No. 421,903, entitled ManuallySet Magnetic Realy" filed Dec. 5, 1973, and copending application Ser.No. 421,904 entitled Push Button" filed Dec. 5, I973, all of thecopending applications having the same assignee as the presentapplication.

BACKGROUND OF THE INVENTION The present invention relates to the fieldof switching devices and, more particularly, is related to a switchingdevice such as a thermal or electromagnetic relay which must be manuallyset before each operation.

It is well known to provide electrical interlocks in systems to preventoperation unless specific conditions have been met. For example. as asafety measure in automobiles, the ignition system may be disabled untilthe driver and all of his passengers have fastened their seat belts. Toimplement such a system, an electrical interlock operated by sensors orswitches sequentially set by the driver and passengers entering the carand fastening the belts may be provided in the ignition system of theautomobile. Unless the belts are fastened after entry, the interlockdisables the ignition system and the engine cannot be started.

It will be recognized that a failure of the electrical interlock systemmay completely disable the ignition system and prevent operation of theautomobile. Such a situation may not only be frustrating to the driverand his passengers but also could prove to be a serious hazardparticularly in an emergency situation in which the automobile must bemoved.

To remedy the situation and eliminate the possible hazards posed by theelectrical interlock it has been suggested that an override relay beprovided to bypass the electrical interlock. The relay must be manuallyset before each override operation and disabled alter operation.Naturally, to prevent repeated use of the relay, it is located in aposition not readily accessible to the driver except in an emergencysituation, and one likely location for the relay is the enginecompartment.

It is, accordingly, a general object of the present invention todisclose a manually set switching device which automatically disablesitself to limit its use to single-cycle or one-time operations.

SUMMARY OF THE INVENTION The present invention resides in a manually setswitching device for one-time operations. The switching device hasparticular utility as an override for an electrical interlock since thedevice must be manually set prior to each use and automatically resetsand disables itself after a single overriding operation.

The switching device is designed to bypass an electrical interlock and,accordingly, the device is comprised of a first switch means forconnection in a load circuit with the electrical interlock. The firstswitch means has a first condition overriding the interlock and a secondcondition permitting the interlock to operate. In the situation in whichthe first switch means is connected in parallel with the interlock, thefirst condition is a closed condition bypassing the interlock and thesecond condition is an open condition permitting the interlock tooperate in its normal fashion.

Manually operable enabling means sets the first switch means in thefirst condition overriding the interlock.

Preferably, the manually operable enabling means holds the first switchin the second condition until it is released to provide trip-freeoperation and to prevent the interlock from being permanently defeatedby fastening manually operable means permantently in its actuatedposition.

Electrically operated disabling means cooperates with the enabling meansto reset the switching device with the first switch means in the secondcondition permitting interlock operation. The electrically operateddisabling means may be an electromagnetic force generator or a thermallyoperated actuator which latches the switching device in a disabledcondition.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an electrical diagramillustrating one embodiment of the manually set switching device of thepresent invention in a typical environment.

FIG. 2 is another electrical diagram similar to FIG. I and illustratesanother embodiment of the manually set switching device in a slightlydifferent environment.

FIG. 3 is a cross-sectional view of one embodiment of the manually setswitching device prior to manual setting or actuation.

FIG. 4 is a cross-sectional view showing the manually set switchingdevice of FIG. 3 during manual actuation.

FIG. 5 is a cross-sectional view similar to FIG. 4 following the manualactuation and during heating of the thermal element.

FIG. 6 is a cross-sectional view similar to FIG. 5 showing the switchingdevice during cooling of the thermal element.

FIG. 7 is a cross-sectional view of another embodiment of the manuallyset switching device prior to manual actuation.

FIG. 8 is a cross-sectional view of the switching device in FIG. 7during manual actuation.

FIG. 9 is a cross-sectional view showing the switching device in FIG. 8during heating of the thermal element subsequent to manual actuation.

FIG. 10 is a cross-sectional view showing the switching device in FIG. 9during cooling of the thermal element.

FIG. 11 is a perspective view of another embodiment of the manually setswitching device having an electrically energized thermal actuator forresetting the device.

FIGS. 11a and 11b is a cross section of an ambient compensation assemblyshown at two different ambient temperatures.

FIG. 12 is a cross-sectional view of the switching device in FIG. 11showing the load contacts open and latched prior to manual setting oractuation and FIG. 13 is a corresponding cross-sectional view showingthe heater contacts at the same time.

FIG. 14 is a cross-sectional view of the device in FIG. 11 showing theload contacts during manual actuation and FIG. 15 is a correspondingcross-sectional view showing the heater contacts at the same time.

FIG. 16 is a cross-sectional view of the device in FIG. 11 showing theload contacts closed following manual actuation and FIG. I7 is acorresponding crosssectional view showing the heater contacts at thesame time.

FIG. I8 is a cross-sectional view of the device in FIG. 11 showing theload contacts closed during cyclic heating and cooling of the thermalelement and FIG. 19 is a corresponding cross-sectional view showing theheater contacts at one instant during the same period.

FIG. 20 is a perspective view of still another embodiment of theswitching device resembling that in FIG. 1 1 but utilizing anelectromagnetic solenoid in place of the heated thermal element.

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an electrical diagramshowing schematically one embodiment of the manually set switchingdevice in the starting circuitry of an automobile having an electricalignition interlock. The interlock normally prevents energization of theelectrical starter motor unless the seat belts in the automobile havebeen properly fastened in each of the occupied seats. It should beunderstood, however, that the switching device of the present inventionmay be employed in other environments to override and interlock orperform other similar functions to which its operation is suited.

The illustrated embodiment of the manually set switching device,generally designated 10, is connected serially in the electricalstarting circuit between the ignition switch 12 and the starter solenoid14 on the starter motor (not shown). A starter switch 16 and the coil 18of the starter relay 20 are also connected in series with the loadswitch 22 within the switching device 10. The ignition switch 12 is, ofcourse, connected to one of the battery terminals, the B+ terminal beingillustrated, and the starter relay 20 and starter solenoid I4 areconnected to the ground terminal through the frame of the automobile.The ignition switch 12 and the starting switch 16 are generallyincorporated in a single housing and are closed sequentially by turningthe ignition key through several index positions. The ignition switch 12is closed first to energize the electrical system of the car and thestarting switch 16 is closed last to pull the starter relay 20 in andenergize the starter solenoid l4 and starter motor. Usually the lastindex position is spring-loaded so that the starting switch 16automatically opens upon release of the key.

The load switch 22 of the switching device is connected in parallel withthe switch 24 of the interlock relay 26 forming part of the seat-beltinterlock system. The system also includes a logic module 28 forenergizing the relay 26 and completing the starting circuitry of theautomobile when certain conditions have been met. The logic module 28receives signals from sensing switches indicating which seats of theautomobile are occupied and which seat belts have been fastened. If theseat belts are first occupied and then the respective seat belts arefastened in that order, a go" signal normally issues from the module toactuate the coil of the interlock 26 and close the relay switch 24. Ifthe logic module detects an unfastened seat belt in an occupied seat orif the sensing switches are not actuated in the proper order, indicatingfor example a permanently buckled seat belt, the interlock relay 26 isnot energized and the starting circuit remains open.

If the logic module 28 is faulty and inoperative, the interlock contactsmay not close and starting of the automobile cannot take place in itsintended fashion. A faulty interlock may be frustrating and dangerous aswell if the automobile must be moved in an emergency situation. In suchcase the manually actuated switching device of the present invention isemployed to bypass the interlock relay 26.

The manually set switching device 10 in FIG. 1 is basically a manuallyset thermal relay in the starting circuitry and overrides the electricalinterlock in a onetime or single-cycle operation. The device 10 iscomprised of the load switch 22 previously described and a manuallyactuated switch 32 serially connected with the heater coil 34 of athermal actuator.

The load switch 22 is normally open and, therefore,

the logic module 28 and interlock relay 26 are enabled to perform thesafety interlock operation for which they are intended. When theinterlock system is inoperative and the automobile must be started inthe absence of a go signal from the interlock logic module 28, the loadswitch 22 is closed and the interlock is disabled or bypassed. Closingof the load switch 22 is accomplished manually. The switch 32 is alsoclosed manually to permit the heater 34 to be energized as soon as theignition switch 12 is turned on. The thermal actuator is connected toboth of the switches 22 and 32 so that deenergization of the actuatorafter the ignition switch 12 is opened leaves the two switches 22 and 32in the open condition. It is thus apparent that the switching device 10must be manually actuated prior to an override operation in order toclose the switch 22. The thermal actuator operated by the heater 34resets the switches 22 and 32 in the condition when they can be openedafter ignition switch 12 is de-energizd so that a subsequent startingoperation cannot be performed unless the interlock relay 26 is operableor switching device 10 is again manually set to enable the load switch22.

FIG. 2 discloses an alternate manually actuated switching device,generally designated 40, connected in parallel with the interlock relay26 in a starting circuit. The elements in FIG. 1 duplicated in FIG. 2bear the same reference numerals. It will be noted that the startingcircuit is slightly different from that shown in FIG. 1 due to theelimination of the starting relay which energized the starter solenoid14. In FIG. 2 the solenoid 14 is energized directly through the loadswitch 22 or the interlock relay 26 when the ignition switch 12 andstarter switch 16 are closed.

The switch 32 in the device 40 is manually actuated or moved to theclosed position to enable the device 40 and disable or override theinterlock relay 26 in the same manner as that described in connectionwith FIG. 1. However, the switch 32 is serially connected with anelectrically energized actuator taking the form of an electromagneticforce generator or solenoid having a coil 42. The solenoid ismechanically connected with the load switch 22 to move the switchbetween open and closed positions. With the ignition switch 12 and themanually actuated switch 32 closed, the switching device 40 is enabledand the coil 42 of the solenoid is electrically energized. When theignition switch 12 is opened to shut off the engine, the solenoid isdeenergized and leaves the switches 22 and 32 open. The switching device40 is, therefore, disabled and the interlock relay 26 is enabled.

It should be understood that the switching devices 10 and 40 are notlimited in application to the specific starting circuits shown in FIGS.1 and 2 respectively, but, may be used interchangable in the twostarting circuits or in other systems employing an electrical interlock.

In the following descriptions of the different embodiments of theswitching device, reference numerals utilized in the electrical diagramsof FIGS. 1 and 2 will be used to identify the corresponding componentsin the device.

FIGS. 36 illustrate one embodiment of the switching device, generallydesignated 50, with the components in different positions assumedsequentially in a single and complete operating cycle.

In FIG. 3 the switching device 50 is shown prior to the manual actuationor setting which initiates an interlock overriding operation. Theswitching device corresponds in electrical structure to the switchingdevice shown in FIG. I. The load switch 22 is formed by twocantilevered, resilient and parallel clapper arms 52 and 54 havingmating electrical contacts adjacent their free ends. The arm 52 carriesan extension which is shown resting upon a slide assembly 56 supportedin the housing 58 for sliding movement to the left and right in FIG. 3.A spring 60 at one end of the assembly 56 biases the assembly intocontact with a manually depressible plunger 62 extending through areturn spring 64 and the housing 58.

The manually actuated switch 32 is formed by contacts mountedrespectively on the free ends of a cantilevered bimetallic arm 66 and acantilevered clapper arm 68. The free end of the arm 68 rests on theslide assembly 56 at the edge of a cutout provided for the arm and itscontact. The heater 34 is formed by a resistive wire wrapped around andelectrically insulated from the bimetallic arm 66 and the arm isconstructed in such a manner that as its temperature is increased by theheater 34, the free end of the arm flexes downwardly and away from theslide assembly 56. Conversely, upon cooling the arm flexes back towardthe slide assembly and assumes the position illustrated at roomtemperature.

FIG. 4 illustrates the switching device 50 during manual actuation. Theplunger 62 is manually depressed and causes the slide assembly 56 toshift to the right as illustrated in opposition to the biasing force ofthe spring 60. As the edge of the cutout on which the clapper arm 68rests moves away from the free end of the arm 68, the arm flexesdownwardly toward the bimetallic arm 66 and closes the contacts of theswitch 32. In the course of the displacement of slide assembly 56, adepending tang 70 on the assembly first encounters a camming surface ona stop 72 attached to the housing 58. The camming surface lifts orflexes the cantilevered end of the slide assembly over the stop 72 andat the same time lifts a latch 74 on the slide assembly over theupwardly projecting tang 76 at the cantilevered end of the bimetallicarm 66. Also, the resilient extension of the clapper arm 52 slides ontothe plunger 62 and thus holds the load switch 22 in the open conditionfor tripfree" operation of the switching device. With trip-freeoperation, the electrical interlock is not permanently defeated byjamming the plunger 62 in the depressed position.

FIG. 5 shows the switching device 50 after the plunger 62 has beenreleased and has been moved out of contact with the slide assembly 56 bythe return spring 64. The resilient extension of clapper arm 52 is nolonger supported by the plunger 62 or the slide assembly 36 and, hence,the load switch 22 closes. The clapper arms 52 and 54 connected inparallel with the electrical interlock relay are, therefore, closed anddisable or bypass the relay.

As shown in FIG. 5 the slide assembly 56 without the restraint of theplunger 62 shifts to the left until the latch 74 and the tang 76 engageone another. The displacement of the slide assembly 56 is not sufficientto open the switch 32 and, therefore, when the ignition switch 12 inFIG. 1 is closed, the heater 34 receives power and raises thetemperature of the bimetallic arm 66. The free end of the arm 66deflects downwardly until it assumes the phantom position illustratedand the latch 74 and tang 76 disengage. At that time the slide assembly56 shifts a further increment to the left until the tang hits the stop72. Continued heating of the bimetallic arm 66 causes further deflectionuntil the switch 32 opens.

FIG. 6 illustrates the switching device 50 after the switch 32 has beenopened and during normal cycling of alternate heating and cooling asswitch 32 opens and closes. The downwardly projecting tang 70 of theslide assembly 56 is in abutment with the stop 72. This condition willbe maintained as long as switch 12 is maintained closed. When ignitionswitch 12 is opened bimetallic arm 66 will cool down and move in anupward direction. It will be observed that the latch 74 has a surfacewhich is engaged by the tank 76 on the bimetallic arm as shown. Furthercooling of the arm 66, therefore, moves the tang 76 upwardly from theposition shown in FIG. 6 and lifts the end of the slide assembly 56upwardly with it so that the tang 70 is lifted over the stop 72. Thereturn spring 60 then urges the slide assembly 56 to the left intoengagement with the plunger 62 and, at the same time, the extension ofclapper arm 52 is lifted upwardly by the assembly to open the loadswitch 22. At this point the components of the switching device 50 arereset in the initial positions shown in FIG. 4 and, as a consequencesubsequent attempts to start the engine of the car will be inhibited bythe disabled switching device unless the mechanically actuated plunger62 is again depressed or the electrical interlock is properly operated.

FIGS. 7-l0 show a switching device, generally designated 80, which is analternate construction of the switching device 50 shown in FIGS. 3-6 andsince the device 80 shares many of the components of the device 50,corresponding parts are identified by the same reference numerals. Theswitching device 80 is, for the most part, identical to the switchingdevice 50 except that the manually actuated switch 32 has beeneliminated and the clapper arm 68 is replaced by a single conductor 82permanently connected with the heater 34. The device 80 is connectedserially in the starting circuit of an automobile in the same manner asthe switching devices 10, 40 or 50 as shown in FIGS. 1, 2 or 3respectively. Accordingly, the load switch 22 is connected in parallelwith the electrical interlock and the circuit including the heater 34 isenergized through the ignition switch of the automobile. Whenever theignition switch is on, the heater 34 is operative.

In FIG. 7 the device 80 is shown prior to manual actuation of theplunger 62. When the plunger is depressed, the cam surface on the stop72 lifts the latch 74 over the upwardly projecting tang 76 on thebimetallic arm 66 to the position shown in FIG. 8. The load switch 22 isheld open to provide trip-free operation of the switching device asdescribed above until the plunger 62 is released as shown in FIG. 9.Without support, therefore, the extension of the clapper arm 52 fallsinto the gap between the plunger 62 and the slide assembly 56 and theload switch 22 closes. Starting of the automobile engine may then takeplace.

As soon as the ignition switch is closed, the heater 34 is energized andthe bimetallic arm 66 flexes downwardly until the tang 76 is disengagedfrom the latch 74 at the position illustrated in FIG. 9 in phantom.Slide assembly 56 then shifts to the left until the tang 70 hits thestop 72.

Continued heating and the downward flexing of the bimetallic element 66while the ignition switch is closed eventually reach an equilibriumcondition. When the ignition switch is finally opened to shut the engineoff, cooling of the arm 66 brings the upwardly projecting tang 76 backinto engagement with a camming surface on the latch 74 as shown in FIG.10 and then lifts the tang 70 over the stop 72. The return spring 60shifts the slide assembly 56 to the left as shown in FIG. 10 and thecomponents of the switching device assume the position shown in FIG. 7with the extension of the clapper arm 52 holding the contacts of loadswitch 22 open to disable the switching device 80 until it is againmanually set.

It will be observed that the switching device 80 provides a minimalperiod, for example 30 seconds, after the ignition switch is opened toagain start or attempt to start the automobile engine independently ofthe electrical interlock. The exact length of the period depends uponthe cooling characteristics of the bimetallic arm, the B+ voltageapplied to the heater, and the temperature reached by the heater 34. Toa greater extent the switching device 50 shown in FIGS. 3-6 provides asimilar but more controlled period as it is adjusted to provide cyclicheating and cooling of the bimetallic arm 66; so that the temperaturereached by the bimetallic arm and hence the duration of the period iscontrolled by the cycling of the heater when the ignition switch isclosed.

FIG. 11 illustrates another embodiment of the switching device of thepresent invention taking the form of a thermal relay which must bemanually set prior to each override operation and which automaticallyresets itself in a disabled condition following an override operation.Like the switching devices 50 and 80 described above, the switchingdevice in FIG. 11, generally designated 90, provides a limited periodfollowing ignition turnoff within which engine starting can be attemptedwithout manually setting the device.

The switching device 90 has the same electrical construction as thatillustrated in the switching device 10 of FIG. 1. The load switch 22completes the starting circuit and the mechanically actuated switch 32is utilized to cyclically energize the heater 34.

All the components of the switching device 90 are mounted on a moldedinsulating base 92 and may be enclosed within a suitable protectivecover attached to the base. The load switch 22 is formed by a pair ofcantilevered and flexibly resilient clapper arms 94 and 96 positioned inoverlying and confronting relationship. The free ends of the arms 94 and96 include mating electrical contacts 98 and 100 respectively and themounted ends of the clapper arms 94 and 96 are riveted to platforms onthe base 92 by means of terminal posts 102 and 104 respectively shownmost clearly in FIG. 12. The lower ends of the terminal posts attach tothe respective connecting pins 106 and 108.

The manually actuated switch 32 for controlling the heater 34 hasbasically the same construction as the load switch 22 and includesoverlying and confronting clapper arms 114 and 116 having matingcontacts 118 and 120 respectively. The clapper arms 114 and 116 areresilient and are mounted in cantilever fashion on the base 92 byterminal posts 122 and 124 respectively as shown in FIG. 13. Aconnecting pin 126 is fastened to the lower end of the terminal post122. The terminal pin 124 is electrically connected to the heater 34.

Mounted on the base 92 adjacent the free ends of the clapper arms 94,96, 114 and 116 is a latch assembly 130. The latch assembly is pivotallymounted in the base 92 on a fulcrum 132 and is biased counterclockwiseabout the fulcrum as viewed in FIGS. 12 and 13 by means of a leaf spring134. The latch assembly includes two latches 140 and 142 which rock withassembly about the fulcrum 132. The latch has a notched upper portionshown most clearly in FIG. 12 which mates with the free end of thecantilevered clapper arm 96 in the unlatched position. In the positionillustrated in FIG. 12 the clapper arm 96 rests on top of the latch 140and the clapper arm 94 extends laterally adjacent the latch with thecontacts 98 and 100 in spaced relationship. Load switch 22 is therefore,open.

The latch 142 shown in FIG. 13 cooperates with the free end of theclapper arm 116 to hold the switch 32 open while the lower clapper arm 114 extends laterally adjacent to the latch. A stop 144 shown mostclearly in FIG. 11 projecting laterally from the latch 142 overlies thefree end of the arm 114 to limit the upward motion of the arm.

FIG. 11 illustrates a manually operated electrically insulating plungerof the switching device 90 slidably mounted in the slots of uprightguide posts 152 and 154. The guide posts may be integrally formed in theinsulating base 92 along with the platforms on which the cantileveredclapper arms 94, 96, 114 and 1 16 are mounted. The guide posts 152 and154 position the manually actuated plunger 150 so that it engages oneend of the latch assembly 130 when the plunger is depressed. Depressingthe plunger causes the latches 140 and 142 to be pivoted about thefulcrum 132 away from the free ends of the clapper arms in opposition tothe leaf spring 134. A plunger return spring 158 shown in FIG. 12attaches to the upper portion of the plunger 150 and normally holds theplunger in the position illustrated out of contact with the latchassembly 130. When the plunger 150 is manually depressed either directlyor by intervening elements such as a push button in a cover enclosingthe thermal relay, the return spring 158 flexes and the lower portion ofthe plunger 150 engages the latch assembly 130 as well as the extensionat the free end of the clapper arm 94.

lnterposed between the two pair of parallel clapper arms 94, 96 and 114,1 16 in FIG. 11 is a thermal actuator including the heater 34 and abimetallic arm 160 riveted in cantilever fashion to a platform of theinsulating base 92 by means of a terminal post 162. A connecting pin(not visible) simialr to the connecting pins 106, 108 in FIG. 12 isconnected to the lower end of the terminal post 162.

Fixedly attached to the free end of the bimetallic arm 160 is atransverse operating rod 164 which has opposite ends extendingrespectively between the clapper arms 94, 96 as shown in FIG. 12 and theclapper arms 114, 116 as shown in FIG. 13. Rod 164 is either ofinsulating material or is insulated relative to the clapper arms.Raising the termperature of the arm 160 by means of the heater 34 causesthe operating rod 164 to lift the clapper arms 96 and 116 above thelatches 140 and 142 and allows the latch assembly 130 to move thelatches under the respective arms. Cooling of the bimetallic arm 160when the heater 34 is turned off lowers the free end of the arm and theoperating rod 164 and depresses the lower clapper arms 94 and 114.

FIGS. 12-19 illustrate the sequence of positons assumed by the swtichingdevice 90 in a complete operating cycle. FIGS. 12, 14, 16 and 18illustrate the clapper arms and contacts of the load switch 22 whileFIGS. l3, l5, l7 and 19 illustrate the respective positions of theclapper arms and contacts of the manually actuated heater switch 32 atthe same times.

FIGS. 12 and 13 illustrate the condition of the switching device 90 inthe disabled condition with the ignition switch of the automobile turnedoff. The thermal actuator formed by the heater 34 and the bimetallic arm160 in FIG. 11 is cool and, thus, the operating rod 164 is in itslowermost position. In FIG. 12 the lower clapper arm 94 is held down bythe operating rod 164 and the upper clapper arm 96 is resting in itslatched position on top of the latch 140 so that the contacts 98 and 100are separated. The load switch 22 is, therefore, open. The leaf spring134 holds the latch assembly in the position illustrated.

In FIG. 13 the lower clapper arm 114 is held down by the operating rod164 and the upper clapper arm 116 is resting on top of the latch 142 sothat the contacts 118 and 120 are separated. The heater switch 32 is,therefore, open.

To initiate overriding of the electricl interlock which would beconnected in parallel with the load switch 22, the manually actuatedplunger 150 is depressed and tilts the latch assembly 130 to theposition shown in FIGS. 14 and 15. In FIG. 14 the latch 140 pivotsclockwise about the fulcrum 132 and the upper clapper arm. 96 dropsdownwardly into the lower notch on the latch as illustrated. At the sametime an extension on the lower clapper arm 94 is engaged by the plunger150 so that the arm 94 is depressed below the position established bythe operating rod 164 and the load contacts 98 and 100 are held open fortrip-free operation. Tripfree operation is desired to prevent theplunger 150 from being permanently jammed in the depressed condition tothereby permanently defeat the electrical interlock.

In FIG. 15 the heater switch 32 is shown at the same time with the freeend of the upper clapper arm 116 out of the latched condition on top ofthe latch 140 and in contact with the lower clapper arm 114 through thecontacts 118 and 120. The heater circuit within the switching device 90is thus closed.

FIGS. 16 and 17 illustrate the load switch 22 and heater switch 32immediately after the manually operated plunger 150 is released andreturned to its uppermost position by the return spring 158 shown inFIG. 12. The load contacts 98 and 100 are closed since the lower clapperarm 94 has flexed resiliently upwardly into contact with the upperclapper arm in the notch of the latch 140. The latch assembly 130 whenreleased by the plunger 150, rotates counter-clockwise in FIGS. 16

and 17 until the upper clapper arms 96 and 116 limit further rotation asillustrated.

At this point in the override operation the ignition switch of theautomobile is turned on and the engine is started through the closedload switch 22 which bypasses the electrical interlock. At the same timethe heater 34 is energized and the free end of the bimetallic arm 160flexes upwardly away from the base 92. The operating rod 164 fixed tothe arm 160 moves upwardly with the arm and carries with it the upperclapper arms 96 and 116 until both of the upper clapper arms are abovethe latches 140 and 142 as illustrated in FIGS. 18 and 19. The lowerclapper arms 94 and 114 being resiliently biased upwardly tend to followthe upper arms 96 and 116 respectively as they are lifted by theoperating rod 164. Both of the switches 22 and 32 remain closedinitially; however, as the clapper arm 116 moves above the latch 142,the clapper arm 114 engages the limit stop 144. Since the heater 34 isstill increasing the temperature of the bimetallic arm 160, theoperating rod 164 continues to lift the upper clapper arm 116 untilcontacts 118 and 120 are broken as illustrated in FIG. 19. Thebimetallic arm 160 then cools down and the operating rod 164 lowersclapper arm 116 until the contacts 118 and 120 close and the heatingcycle is repeated. As long as the ignition switch of the automobile isclosed, the cyclic heating and cooling of the bimetallic arm 160continues and contact between the clapper arms 114 and 116 is made andbroken. At the same time clapper arms 94 and 96 oscillate up and downtogether and the arm 96 remains above the latch 140. The load switch 22,therefore, remains closed and the automobile engine can be started asoften as required.

When the ignition switch is finally opened to stop the automobileengine, current through the heater 34 is terminated, the bimetallic arm160 cools to ambient temperature and the operating rod 164 returns tothe position illustrated in FIGS. 12 and 13. The upper class arms 96 and1 16 move into the latched positions on top of the latches and 142 whilethe operating rod 164 depresses the lower clapper arms 94 and 114 andopens the contacts forming the switches 22 and 32. With the heaterswitch 32 open, subsequent energization of the relay through theignition switch of the automobile has no effect and, therefore, theswitching device 90 is disabled with the load switch 22 open to permitthe electrical interlock to perform its intended function.

It will be observed that the cooling time of the bimetallic arrmprovides a brief period, for example 30 seconds to 1 minute, after theignition switch is turned off within which the engine can be restartedwithout having to manually reset the switching device 90. This intervalis advantageous since it allows the engine to be restarted after amomentary or possibly inadvertent shutting off of the engine.

In the several thermal switches described above it may be desirable toprovide ambient compensation for the bimetallic member, for example inorder to obtain more consistent timing for resetting. An exemplarystructure is shown in FIGS. 11a and 11b in which the bimetallic arm 160of FIG. 11 is mounted on another bimetallic am 161 having its high andlow coefficient of expansion layers reversed relative to arm 160. Arms160, 161 are joined by a relatively inflexible member 163. It will benoted that there is a distance d between rod 164 and base 92 which doesnot change from a first ambient temperature (FIG. 11a) and a secondhigher ambient temperature (FIG. 11b) since the deflection of bimetallicarm 161 offsets the deflection of bimetallic arm 160.

FlG. 20 illustrates still another embodiment of a switching device,generally designated 170. The device 170 is constructed in a mannersimilar to the device 90 and hence corresponding elements bearcorresponding reference numberals. The principal distinction between thedevices 90 and 170 is that an electromagnetic force generator oractuator taking the form of a solenoid 172 replaces the thermal actuatorformed by the bimetallic arm 160 and heater 134 in FIG. 11. Theelectrical dia gram of the switching device 170, accordingly,corresponds to the device 40 shown in FIG. 2.

The solenoid 172 includes the coil 42 illustrated electrically in FIG. 2and a U-shaped ferromagnetic support bracket 174 about which the coil 42is wound. The bracket 174 is riveted at one end to the insulating base92 by a terminal post 176 so that the opposite end of the bracketextends in cantilever fashion over the base 92. in addition, a clapper178 is sandwiched between the base 92 and the bracket 174 at theterminal post 176 and extends in cantilever fashion relative to the base92 and under the coil 42 so that in its unflexed condition a small gapexists between the free end of the clapper and the closely adjacent freeend of the bracket 174. One lead (not shown) from the coil 42 isconnected to a terminal 176 which has a connecting pin similar to thepins 106 and 108, and the other lead (not shown) from the coil leads tothe terminal post 124. As a consequence, the switch 32 controls theenergization and de-energization of the solenoid when the ignitionswitch 12 in FIG. 2 is turned on.

Extending transversely across the free end of the clapper 178 is aninsulating or insulated operating rod 180. The operating rod 180 extendsunderneath both sets of parallel upper arms 94, 96 and 1 14, 116 andlifts the upper clapper arms 96 and 116 above the latches 140 and 142respectively when the solenoid is energized. Energization of thesolenoid, of course, cannot take place until the switch 32 is closed andthis occurs when the manually actuated plunger 150 trips the latches 140and 142 to allow the free ends of the clapper arms 114 and 116 to makeelectrical contact. Although desirable, it is not essential to have theclapper arms 94 and 96 make electrical contact when the latch 140 isreleased since the energizing of the solenoid 172 is certain to pull thefree ends of the clapper arms 94 and 96 into contact as the arm 96 islifted above the latch 140.

Release of the clapper arms from the latched position is otherwiseidentical in operation to that described in connection with FIGS. 12-17including the trip-free operation produced by the engagement of themanually actuated plunger 150 and clapper arm 94. When the solenoid 172is energized and has lifted the clapper arms above latches 140 and 142,no cycling operation equivalent to that described in connection withFIG. 19 takes place so that the solenoid 172 remains energized as longas the ignition switch 12 is closed. When the ignition switch opens, theupper clapper arms 94 and 1 16 are left in the latched condition and theentire switching device 170 is disabled until it is again manually setfor an override operation.

While the present invention has been described in several preferredforms, it should be understood that still other modifications andsubstitutions to the specific structures shown can be had withoutdeparting from the spirit of the present invention. For example, latchassembly 130 and the cooperating manually operated plunger may takeforms other than that specifically illustrated as long as the latch 142performs the latching function upon the switch 32 and disables theswitching device when electrical power from the ignition switch isremoved from the device. The load switch 22 formed by the clapper arms94 and 96 need not necessarily be operated between a latched andunlatched condition provided that the arms acquire a normally opencondition when the actuator, that is either the thermal actuatorillustrated in the device 90 or the electromagnetic actuator illustratedin the device 170, is de-energized. In such case the actuator pulls theclapper arms 94 and 96 closed when the actuator is energized through theswitch 32. Accordingly, the switching device of the present inventionhas been described in several different embodiments by way ofillustration rather than limitation.

We claim: 1. A manually set switching device comprising: first switchmeans having an enabling switch condition and an overriding switchcondition and operatively connectible to a load circuit; electricallyenergized force generating means operatively connected to the firstswitch means for moving the first switching means between the two switchconditions; second switch means having enabling and disabling switchconditions and coupled with the electrically operated force generatingmeans to control the en ergization and deenergization of the forcegenerating means; latch means operatively engagable with the secondswitch means for holding the second switch means in the disabling switchcondition upon deenergization of the force generating means; andmanually operable actuator means for disengaging the second switch meansfrom the latch means. 2. A manually set switching device as in claim 1wherein:

the force generating means is also operatively connected with the secondswitch means for moving the second switch means into the disablingswitch condition on the latching means. 3. A manually set switchingdevice as in claim 1 wherein:

the latching means is also operatively engagable with the first switchmeans for holding the first switch means in the enabling switchcondition upon deenergization of the force means. 4. A manually setswitching device for bypassing an electrical interlock in a one-timeoperation comprising:

first switch means having an enabling switch condition and an overridingswitch condition and operatively connectible to a load circuit inparallel with an electrical interlock to correspondingly enable oroverride the interlock; electrically energized force generating meansoperatively connected to the first switch means for moving the firstswitching means between the two switch conditions; second switch meanshaving enabling and disabling switch conditions and coupled with theelectrically operated force generating means to control the en- 13ergization and deenergization of the force generating means;

latch means operatively engagable with the second switch means forholding the second switch means in the disabling switch condition upondeenergization of the force generating means; and

manually operable actuator means for disengaging the second switch meansfrom the latch means.

5. A manually set switching device as in claim 4 herein:

the force generating means is also operatively connected with the secondswitch means for moving the second switch means into the disablingswitch condition on the latching means.

6. A manually set switching device as defined in claim 4 wherein:

the electrically energized force generating means comprises anelectrically heated thermal actuator.

7. A manually set switching device as in claim 6 wherein the thermalactuator comprises an electrical heater and a bimetallic thermal elementadjacent the heater.

8. A manually set switching device as in claim 6 herein:

the force generating means is also operatively connected to the secondswitch means to move the second switch means onto the latching means.

9. A manually set switching device as in claim 4 wherein:

the latching means is also operatively engagable with the first switchmeans for holding the first switch means in the enabline switchcondition upon deenergization of the force generating means.

10. A manually set switching device as defined in claim 4 wherein:

the electrically energized force generating means comprises anelectromagnetic force generator having a coil.

11. A manually enabled relay comprising:

a first pair of cantilevered clapper arms positioned with the free endsof the arms in confronting relationship and forming a first switch;

a second pair of cantilevered clapper arms positioned with the free endsof the arms in confronting relationship and forming a second switch;

a movable latch engagable with the free end on one arm of at least oneof the pairs to hold the arms of the pair apart;

an electrically energized actuator means connected with the arms of eachpair to move the arms of the respective pairs in and out of contact andto move the free end of the one arm of at least said one of the pairsonto the movable latch; and

a manually operated actuator means engagable with the movable latch forunlatching the free end of the one arm.

12. A manually enabled relay as in claim 11 wherein the movable latch isengagable with the free end of the one arm of each of the first andsecond pairs.

13. A manually enabled relay as in claim 11 wherein:

the one clapper arm of the first pair is engaged by the movable latch ina latched position of the arm the electrically energized actuator meansand the clapper arms of the first pair are electrically connected toplace the electrical actuator and the first switch in series.

14. A manually enabled relay as in claim 13 wherein:

the electrically energized actuator means comprises an electricallyheated bimetallic element positioned to lift the free end of said onearm ofthe first pair onto the latch when the bimetallic element isheated. 15. A manually enabled relay as in claim 14 wherein: thebimetallic element is positioned when not heated to hold the otherclapper arm of the first pair out of contact with the one arm of thefirst pair in the latched position. 16. A manually enabled relay as inclaim 11 wherein: the electrically energized actuator means comprises anelectromagnetic solenoid engaging the clapper arms of the first andsecond pair. 17. A manually enabled relay as in claim 11 wherein: themanually operated actuator means has a first position relative to themovable latch permitting the latch to hold the one arm in a latchedcondition and a second position holding the latch and the one armunlatched, and the manually operated actuator means in the secondposition engages and holds the respective clapper arms of the first andsecond pairs apart. 18. A manually enabled relay as in claim 17 wherein:the second switch formed by the second pair of clapper arms iselectrically connected with the electrically energized actuating means.19. A manually enabled relay as defined in claim 11 wherein:

the electrically energized actuator means is mechanically connected withthe second switch to move one of the clapper arms of the switch onto themovable latch out of contact with the other clapper arm of the switch,and is electrically connected in series with the second switch. 20. Amanually enabled relay as in claim 19 wherein: the manually operatedactuator means includes a depressible plunger operatively engagable withthe movable latch and with the first switch to hold the clapper armsapart when the plunger is depressed. 21. A manually set magnetic relaycomprising: first switch means having open and closed switch conditions;electromotive force generating means including a coil operativelyconnected to the first switch means for moving the first switch meansbetween the switch conditions; second switch means having open andclosed switch conditions and serially coupled to the coil of theelectromotive force generating means to permit energization andde-energization of the coil; latch means operatively engagable with saidsecond switch means for holding the second switch means in the open andlatched condition; the electromotive force generating means also beingoperatively connected to the second switch means to move the secondswitch means to the open and latched condition; and f manually operableactuator means for disengaging the second switch means and the latchingmeans. 22. A manually set magnetic relay as in claim 21 wherein:

the latch means is also engagable with the first switch means forholding the first switch means in the open and latched condition. 23. Amanually set magnetic relay as in claim 22 wherein:

the first switch means and the second switch means are each comprised ofa pair of parallel and resilient clapper arms; and the clapper arms ofthe second switch means assume the closed condition in the unlatchedcondition.

i i i

1. A manually set switching device comprising: first switch means havingan enabling switch condition and an overriding switch condition andoperatively connectible to a load circuit; electrically energized forcegenerating means operatively connected to the first switch means formoving the first switching means between the two switch conditions;second switch means having enabling and disabling switch conditions andcoupled with the electrically operated force generating means to controlthe energization and deenergization of the force generating means; latchmeans operatively engagable with the second switch means for holding thesecond switch means in the disabling switch condition upondeenergization of the force generating means; and manually operableactuator means for disengaging the second switch means from the latchmeans.
 2. A manually set switching device as in claim 1 wherein: theforce generating means is also operatively connected with the secondswitch means for moving the second switch means into the disablingswitch condition on the latching means.
 3. A manually set switchingdevice as in claim 1 wherein: the latching means is also operativelyengagable with the first switch means for holding the first switch meansin the enabling switch condition upon deenergization of the force means.4. A manually set switching device for bypassing an electrical interlockin a one-time operation comprising: first switch means having anenabling switch condition and an overriding switch condition andoperatively connectible to a load circuit in parallel with an electricalinterlock to correspondingly enable or override the interlock;electrically energized force generating means operatively connected tothe first switch means for moving the first switching means between thetwo switch conditions; second switch means having enabling and disablingswitch conditions and coupled with the electrically operated forcegenerating means to control the energization and deenergization of theforce generating means; latch means operatively engagable with thesecond switch means for holding the second switch means in the disablingswitch condition upon de-energization of the force generating means; andmanually operable actuator means for disengaging the second switch meansfrom the latch means.
 5. A manually set switching device as in claim 4wherein: the force generating means is also operatively connected withthe second switch means for moving the second switch means into thedisabling switch condition on the latching means.
 6. A manually setswitching device as defined in claim 4 wherein: the electricallyenergized force generating means comprises an electrically heatedthermal actuator.
 7. A manually set switching device as in claim 6wherein the thermal actuator comprises an electrical heater and abimetallic thermal element adjacent the heater.
 8. A manually setswitching device as in claim 6 wherein: the force generating means isalso operatively connected to the second switch means to move the secondswitch means onto the latching means.
 9. A manually set switching deviceas in claim 4 wherein: the latching means is also operatively engagablewith the first switch means for holding the first switch means in theenabline switch condition upon de-energization of the force generatingmeans.
 10. A manually set switching device as defined in claim 4wherein: the electrically energized force generating means comprises anelectromagnetiC force generator having a coil.
 11. A manually enabledrelay comprising: a first pair of cantilevered clapper arms positionedwith the free ends of the arms in confronting relationship and forming afirst switch; a second pair of cantilevered clapper arms positioned withthe free ends of the arms in confronting relationship and forming asecond switch; a movable latch engagable with the free end on one arm ofat least one of the pairs to hold the arms of the pair apart; anelectrically energized actuator means connected with the arms of eachpair to move the arms of the respective pairs in and out of contact andto move the free end of the one arm of at least said one of the pairsonto the movable latch; and a manually operated actuator means engagablewith the movable latch for unlatching the free end of the one arm.
 12. Amanually enabled relay as in claim 11 wherein the movable latch isengagable with the free end of the one arm of each of the first andsecond pairs.
 13. A manually enabled relay as in claim 11 wherein: theone clapper arm of the first pair is engaged by the movable latch in alatched position of the arm the electrically energized actuator meansand the clapper arms of the first pair are electrically connected toplace the electrical actuator and the first switch in series.
 14. Amanually enabled relay as in claim 13 wherein: the electricallyenergized actuator means comprises an electrically heated bimetallicelement positioned to lift the free end of said one arm of the firstpair onto the latch when the bimetallic element is heated.
 15. Amanually enabled relay as in claim 14 wherein: the bimetallic element ispositioned when not heated to hold the other clapper arm of the firstpair out of contact with the one arm of the first pair in the latchedposition.
 16. A manually enabled relay as in claim 11 wherein: theelectrically energized actuator means comprises an electromagneticsolenoid engaging the clapper arms of the first and second pair.
 17. Amanually enabled relay as in claim 11 wherein: the manually operatedactuator means has a first position relative to the movable latchpermitting the latch to hold the one arm in a latched condition and asecond position holding the latch and the one arm unlatched, and themanually operated actuator means in the second position engages andholds the respective clapper arms of the first and second pairs apart.18. A manually enabled relay as in claim 17 wherein: the second switchformed by the second pair of clapper arms is electrically connected withthe electrically energized actuating means.
 19. A manually enabled relayas defined in claim 11 wherein: the electrically energized actuatormeans is mechanically connected with the second switch to move one ofthe clapper arms of the switch onto the movable latch out of contactwith the other clapper arm of the switch, and is electrically connectedin series with the second switch.
 20. A manually enabled relay as inclaim 19 wherein: the manually operated actuator means includes adepressible plunger operatively engagable with the movable latch andwith the first switch to hold the clapper arms apart when the plunger isdepressed.
 21. A manually set magnetic relay comprising: first switchmeans having open and closed switch conditions; electromotive forcegenerating means including a coil operatively connected to the firstswitch means for moving the first switch means between the switchconditions; second switch means having open and closed switch conditionsand serially coupled to the coil of the electromotive force generatingmeans to permit energization and de-energization of the coil; latchmeans operatively engagable with said second switch means for holdingthe second switch means in the open and latched condition; theelectromotive force generating means also being operatively connected tothe second switch means to move the seCond switch means to the open andlatched condition; and f manually operable actuator means fordisengaging the second switch means and the latching means.
 22. Amanually set magnetic relay as in claim 21 wherein: the latch means isalso engagable with the first switch means for holding the first switchmeans in the open and latched condition.
 23. A manually set magneticrelay as in claim 22 wherein: the first switch means and the secondswitch means are each comprised of a pair of parallel and resilientclapper arms; and the clapper arms of the second switch means assume theclosed condition in the unlatched condition.